• PDF support (see #683 (comment))
• PDF: scroll reading content by screen height (not by page) by tap on top | bottom tap zones
• PDF: zoom and shift blocking
• PDF: save zoom and shift per article (book)
• PDF: long tap on bottom tap zone toggles black and white background
• Article screen: control panel with most popular actions by tap on central tap zone (the whole menu is accessible by ↓ button)
• Article screen control panel: seek bar for quick navigation on needed page
• fix for #952